//得到随机的颜色值
function randomColor() {
  let r = Math.floor(Math.random() * 256)
  let g = Math.floor(Math.random() * 256)
  let b = Math.floor(Math.random() * 256)
  return 'rgb(' + r + ',' + g + ',' + b + ')'
}

function draw(canvas) {
  let show_num = []
  let canvas_width = canvas.width
  let canvas_height = canvas.height
  let context = canvas.getContext('2d') //获取到canvas画图的环境，演员表演的舞台

  const sCode =
    'a,b,c,d,e,f,g,h,i,j,k,m,n,p,q,r,s,t,u,v,w,x,y,z,A,B,C,E,F,G,H,J,K,L,M,N,P,Q,R,S,T,W,X,Y,Z,1,2,3,4,5,6,7,8,9,0'
  const aCode = sCode.split(',')
  const aLength = aCode.length //获取到数组的长度

  for (let i = 0; i < 4; i++) {
    //这里的for循环可以控制验证码位数（如果想显示6位数，4改成6即可）
    let j = Math.floor(Math.random() * aLength) //获取到随机的索引值
    // let deg = Math.random() * 30 * Math.PI / 180;//产生0~30之间的随机弧度
    let deg = Math.random() - 0.5 //产生一个随机弧度
    let txt = aCode[j] //得到随机的一个内容
    show_num[i] = txt.toLowerCase()
    let x = 10 + i * 20 //文字在canvas上的x坐标
    let y = 20 + Math.random() * 8 //文字在canvas上的y坐标
    context.font = 'bold 23px 微软雅黑'

    context.translate(x, y)
    context.rotate(deg)

    context.fillStyle = randomColor()
    context.fillText(txt, 0, 0)

    context.rotate(-deg)
    context.translate(-x, -y)
  }

  for (let i = 0; i <= 5; i++) {
    //验证码上显示线条
    context.strokeStyle = randomColor()
    context.beginPath()
    context.moveTo(Math.random() * canvas_width, Math.random() * canvas_height)
    context.lineTo(Math.random() * canvas_width, Math.random() * canvas_height)
    context.stroke()
  }

  for (let i = 0; i <= 30; i++) {
    //验证码上显示小点
    context.strokeStyle = randomColor()
    context.beginPath()
    let x = Math.random() * canvas_width
    let y = Math.random() * canvas_height
    context.moveTo(x, y)
    context.lineTo(x + 1, y + 1)
    context.stroke()
  }

  return show_num
}

export default draw
